This invention relates to a film for shielding electronic devices, such as, computers, communication devices, printers, video cameras, and the like, from emitting electromagnetic radiation (EMI).
Electronic devices emit electromagnetic radiation that can interfere with television, radio, and other communications. The level of EMI is regulated by governments, and consequently the manufacturers of electronic devices are required to limit the level of EMI produced by their devices. A second reason for limiting EMI is that stray signals within a device can cause internal interference or cross-talk. Two approaches are used currently to limit EMI: suppressing the electromagnetic radiation at the source, or containing the radiation so that it does not escape the device.
Containment can be accomplished per Faraday's principle by enclosing the emitting device in a perfectly conducting shield, such as, a metallic can or a conformal coating. However, the metallic can is less than optimum because there are always areas from which radiation can escape, it adds cost and weight to the electronic device, and it is not suitable for a flexible substrate. Moreover, if rework is needed, the metallic can must be de-soldered and then re-soldered, which increases the risk of damaging active devices.
Conformal coatings also have disadvantages. They are typically applied in multiple layers, a dielectric insulating layer and a conductive layer, which require multiple processing steps. The conductive layer is usually applied as a liquid ink and if not carefully controlled may lead to deposition in an undesired area and cause shorts in the circuitry. The drying/curing time for printed conductive inks is in the range of 10 to 30 minutes, longer than desired, and conductive inks may contain volatile organic solvent. The dielectric layer is interposed between the conductive layer and the circuitry to prevent the conductive layer from electrically contacting predetermined areas of the circuitry and substrate.
In order to overcome the current disadvantages of EMI shielding, the instant invention is disclosed and claimed.